When a Marine known for his practical jokes is found dead on Halloween Eve, the NCIS team discovers that the victim's "good-natured" pranks may have inspired ghoulish retribution. Meanwhile, Ziva tries to adjust to her new role on the team.

While on the flight back from Paris, Tony and Ziva realize that their assignment to protect a government witness in an embezzlement case is in great danger when they learn that an assassin is located on the same flight.